Coaxial switch

ABSTRACT

A switch adapted for as an A-B coaxial cable switch for CATV systems. The switch includes a pair of depressible pushbuttons, one for each cable. The buttons always move oppositely to each other. The crossbar extends diagonally within the switch and pivots at its center on a stationary slot in the switch housing. The ends of the crossbar pivot on slots in longitudinally reciprocable bars connected to the pushbuttons. A pair of coil springs are connected between the ends of the crossbar and the housing. Movable contact members carried by the bars make or break brushing contact with stationary spring contacts each time the pushbuttons are switched. When either button is depressed to move the crossbar past center or lateral position, the coil springs urge the crossbar toward the reverse position.

D United States Patent [151 3,648,000 Thompson 1 Mar. 7, 1972 [54]COAXIAL SWITCH 3,273,098 9/1966 Saito ..333/32 X [72] Invemor: John R.Thompson, 7355 Fuhon Avenue, 3,182,270 5/1965 Horton ..333/7 R NorthHollywood cahf' 91605 Primary Examiner-David Smith, Jr. [73] Assignee:Electronic Industrial Engineering, Inc., y Comslock North Hollywood,Calif. [57] ABSTRACT [22] Filed: Aug. 26, 1970 A switch adapted for asan A-B coaxial cable switch for [21] Appl- 66,994 CATV systems. Theswitch includes a pair of depressible pushbuttons, one for each cable.The buttons always move op- 52 us. Cl. ..200/153 s, 200/67 A, 200/72,Psitely each The mssbar extends diagmany within 333/97 the switch andpivots at its center on a stationary slot in the [51] Int. Cl. ..H0lp1/10 switch housing The ends of the crossbar Pivo slots in [58] Field ofSearch ..260/153 s, 67 B, 69, 71, 72, gitudinally iecipmcable bars mutedthe pushbumms' A 260/757 503; 333/97 5 7 336/105 pair of coil springsare connected between the ends of the crossbar and the housing. Movablecontact members carried [56] References Cited by the bars make or breakbrushing contact with stationary spring contacts each time thepushbuttons are switched. When UNITED STATES PATENTS either button isdepressed to move the crossbar past center or lateral position, the coilsprings urge the crossbar toward the 2,498,907 2/1950 Atwood ..200/153 Srevel-Se position 2,420,066 5/1947 Conway 3,327,253 6/ 1967 Campbell..333/32 X 8 Claims, 6 Drawing Figures Patented March 7, 1972 z 2Sheets-Sheet 2 60 FIG.

Y/A/ l ENTOR JOHN R. THOMPSON ROBERT C. Co/vzs TOCK A 7'7'01QA/EYcoxxmr. swr'rcrr BACKGROUND OF THE INVENTION l. Field of the InventionThe invention relates to a coaxial switch which is particu- SUMMARY OFTHE INVENTION The invention comprises a switch of the type describedwhich is an improvement over the prior art because it provides increasedisolation of the respective cables. The switch is guaranteed to providea minimum of 75 db. isolation and is believed in fact to providesubstantially more.

Another advantage of the switch is that it is extremely rugged in itsstructure and operation, is substantially foolproof and will last for anextremely long time. It is substantially impossible to damage or breakthe switch, even by pushing both buttons at the same time. The switch isalso more economical to manufacture because of its simplicity in partsand assembly.

The contact elements make a brushing engagement with each other over anextremely large surface area each time they make or break contact, sothat clean and secure contacts are achieved.

In an alternative embodiment, the switch incorporates a transformerwithin the switch housing, eliminating the necessity of a separateoutput transformer.

It is accordingly among the objects of the invention to provide a switchhaving all of the advantages and benefits set forth above. The inventionalso comprises such other objects, advantages and capabilities as willlater more fully appear and which are inherently possessed by theinvention.

While I have shown in the accompanying drawings a preferred embodimentof the invention, it should be understood that the same is susceptibleof modification and change without departing from the spirit of theinvention.

REF ERRING TO THE DRAWINGS FIG. 1 is an isometric view of the switch ona reduced scale;

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1;

FIG. 3 is a sectional view taken on line 33 of FIG. 2;

FIG. 4 is a sectional view taken on line 4-4 of FIG. 2;

FIG. 5 is a sectional view similar to FIG. 2 of an alternativeembodiment;

FIG. 6 is an end view of the switch of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment which hasbeen selected to illustrate my invention comprises a substantiallysquare housing 10, which may conveniently be formed of cast metal. Thetop of the housing is provided with a cover 11. The interior of thehousing is divided into a plurality of small compartments which housethe various component parts of the switch.

Extending outwardly from the backwall of the housing 10 are three cableferrules 12, 13 and 14, the outside of which is electrically grounded tothe housing 10. The ferrules have hollow interiors for receiving thecenter conductors of the cable, which is not shown in the drawings.

The rear portion of the housing 10 is divided into five adjacentcompartments. The hollow interiors of the ferrules 12, 13 and 14 arealigned with openings leading into the two corner compartments 15 and 16and the center compartment 17. Mounted within the compartments 15-17 aresubstantially square plugs 18-20 respectively, each of which comprises aplurality of pieces of relatively hard electrically nonconductivematerial such as plastic.

The plug 19 in the center compartment 17 holds in place a pair ofelongated spring contacts 21 and 22, the outer ends of which formreversely bent loops having straight parallel portions which are adaptedto resiliently receive and make secure electrical contact with a cableinserted into the center ferrule 13. The inner ends of the springcontacts 21 and 22 are free and extend inwardly adjacent to each otherinto an open area 50 of the housing 10 which is disposed forwardly fromthe compartments 15 and 17. The tips of the inner ends of the contacts21 and 22 are bent both reversely and in opposite directions away fromeach other.

The plug 18 in the corner compartment 15 holds in place a pair ofelongated spring contacts 23 and 24, the outer ends of which formreversely bent loops having straight parallel portions which are adaptedto removably receive and make secure electrical contact with a cableinserted into the end ferrule 12. Only the contact 24 has a free innerend which extends inwardly into the free area 50 of the housing. The tipof the free inner end of the contact 24 is reversely bent.

The plug 18 also holds in place a 75 ohm resistor 25, the rear lead ofwhich is bent around the back of the plug 18 to make electrical contactwith the adjacent inner wall of the housing 10. The other lead of theresistor 25 extends into the free area 50 and is bent around the edge ofa portion of the plug 18 which also protrudes inwardly into the freearea 50. The contact 24 is resiliently biased so that it is normallyurged into physical and electrical contact with the adjacent lead of theresistor 25.

The plug 20 in the other comer compartment 17 holds in place a pair ofidentical spring contacts 26 and 27, which are adapted to make contactwith a cable inserted into the other ferrule 14. An identical 75 ohmresistor 28 is held in an identical manner and the contact 27 isresiliently biased into contact with the adjacent lead of the resistor28.

The forward end of the housing 10 is divided into a pair of opencompartments 29 and 30. These compartments are adapted to receive a pairof pushbuttons 31 and 32, which are mounted for reciprocal movementtoward and away from the housing 10. The pushbuttons 31 and 32 movealternately to each other. When the pushbuttons 31 and 32 are in inwardclosed position, they are disposed substantially entirely within thecompartments 29 and 30. When they are in their outward open positions,they protrude forwardly substantially entirely beyond the forward wallof the housing 10.

Extending rearwardly into the housing 10 from the pushbuttons 31 and 32are a pair of vertically directed bars 33 and 34 respectively, whichextend through a pair of compartments 35 and 36 disposed directly behindthe compartments 29 and 30 and into the open area 50. The bars 33 and 34slidably extend through slots cut in the laterally directed walls of thecompartments 35 and 36.

The inner ends of the bars 33 and 34 which are disposed within the openarea 50 carry a pair of elongated leaf spring contact members 37 and 38respectively. Each of these contact members includes a pair of laterallydirected wings, which are gradually bent inwardly at their outer ends.

The wall which divides the compartments 35 and 36 is provided with acentral slot 39, the opposite edges of which are V- shaped to form apair of oppositely facing fulcrums for a crossbar 40, which pivotallyextends through the slots 39. The crossbar 40 also pivotally extendsthrough a pair of slots 41 and 42, which extend downwardly into theupper part of the bars 33 and 34. The opposite edges of the slots 41 and42 are also V-shaped to form a pair of oppositely facing fulcrums forpivotal movement of the crossbar 40.

Connected to the opposite ends of the crossbar 40 are the inner ends ofa pair of coil springs 43 and 44, the outer ends of which are attachedto the housing 10 adjacent to the center of the sidewalls of thecompartments 35 and 36.

It will be seen that the switch is in a stable condition only when oneof the pushbuttons 31 and 32 is in closed position and the other is inopen position.

When the pushbutton 31 is in closed position, its contact member 37engages the spring contacts 21 and 24. In doing so, it holds the contactmember 24 away from contact with the adjacent lead of the resistor 25.

The pushbutton 32 is then in open position, with the wings of itscontact member 38 engaging and making electrical contact with theforward wall of the open area 50. This grounds the contact member 38 andprevents it from acting as an antenna or radiator of signals. Thisaccordingly adds to the isolation of the cables. The contact member 27is at this time in engagement and electrical contact with the adjacentlead to the resistor 28.

When manual pressure is exerted upon the pushbutton 32 to move itinwardly toward closed position, such movement is resisted by both ofthe coil springs 43 and 44. As the pushbutton 32 and its bar 3 tmoveinwardly, the crossbar 40 is pivoted from an angular to a lateralposition, causing both of the coil springs 43 and 44 to becomecompressed. As soon as the crossbar 40 moves past the center or lateralposition, both of the coil springs 43 and 44 urge the crossbar 4l0onwardly to the opposite angular position. They quickly move thepushbuttons 31 and 32 on to opposite positions without further manualpressure.

It will be seen that as the contact member 38 of the bar 34 movesrearwardly across the open area 50, it engages the contacts 22 and 27and bends them with what may be termed a brushing action in which thegradually curved outer ends of the contact member 38 brush across andthen form a large contact area with the bent ends of the contacts 22 and27. There is a similar brushing action in reverse when the contactmember 38 moves back toward open position. There is identi cal brushingaction of the other contact member 37 as it moves into and out ofengagement with the contacts 21 and 24.

When the contact member 27 is bent by its engagement with the contactmember 38, it moves inwardly away from contact with the adjacent lead ofthe resistor 28. On the other side of the housing, the opposite movementtakes place. As the contact member 37 moves outwardly, the contact 24 byits own resilience moves back into engagement with the adjacent lead ofthe resistor 25.

The switch is particularly adapted for use as an A-B coaxial switch inCATV systems. it is capable of other uses as well, such as televisionstation switching. The functional structure of the switch is alsocapable of being used for substantially any electrical switchingapplication.

When the switch is used as an A-B coaxial switch, the pushbuttons 31 and32 are marked A" and 3" respectively. The ferrules l4 and arc markedCable A" and Cable B" respectively. The center ferrule is marked TV."The cables A and B are connected to their respective ferrules and the TVset is connected to the center ferrule 13.

The TV set can then be switched from either cable to the other by merelypushing one or the other of the push buttons 31 and 32. This doubles thenumber of channels available to the TV set user on a CATV system.

The interior of the switch is preferably provided with a thinsubstantially flat copper shield 45, which covers the switch contactarea and which acts as an electrostatic shield. The switch may beremovably mounted in a plastic outer cover 46, which is preferablysomewhat resilient. The cover 46 protects the switch from possiblephysical damage and also provides shock hazard protection.

It will be noted that the resistors 25 and 28 provide a 75 ohmtermination for the unused input cable.

In use, the switch is preferably mounted on or near the television seteither through adhesive or with fastening members such as screws or thelike.

The ferrules l2, l3 and 14 may be replaced by any type of commonly usedcoaxial cable connector, such as a female F connector common to CATVsystems, or any other suitable connector.

FIGS. 5 and o of the drawings show an alternative embodiment of theinvention in which a balun transformer is physically integrated withinthe housing of the switch. This eliminates the necessity of providing aseparate output transformer between the switch and the television set.Such a transformer is required because the coaxial cable is anunbalanced 75 ohm system and the television set requires a 300 ohmbalance input. The transformer accordingly serves as an impedancematching device and converts an unbalanced system to a balanced system.

The structure and operation of the switch itself is identical with thatof the embodiment previously described. The same reference numerals areaccordingly used for identical parts. In this embodiment, however, thecontact elements 2i and 22 are connected to one of the loads of theprimary side of a balun transformer 60 through a first DC blockingcapacitor 61. The opposite primary lead of the transformer is connectedto one lead of a second DC balancing capacitor 62. the opposite end ofwhich is grounded to the housing.

The secondary of the transformer 61 is connected to a pair of screws 63and 64, which are adapted to be connected to the antenna input of thetelevision set. The center lead of the transformer secondary iselectrically grounded by means not shown in the drawings.

it may be noted that in both embodiments of the invention the housingand all ofits component walls are preferably made of metal or otherelectrically conductive material. All of the switch elements within thehousing except the contact members, leads and springs are preferablymade of hard plastic or other electrically nonconductive material. Thesprings are isolated in separate compartments to minimize anydeleterious effect which they might have in preventing isolation.

I claim:

ll. A switch comprising a housing, first and second pushbuttons mountedfor alternating manual reciprocal movement between inward and outwardpositions with respect to said housing, an elongated bar attachment toeach of said pushbuttons, said bars extending inwardly into said housingfrom said pushbuttons, a crossbar having its center pivotally mounted ona stationary part of said housing, the ends of said crossbar beingpivotally connected to said bars, a contact member carried by the innerend of each of said bars, at least one substantially stationary contactadapted it be engaged by each of said contact members when thepushbutton to which it is attached is in inward position, said crossbarbeing movable upon the inward movement of either of said pushbuttonsbetween two stable diagonal positions, in one of which said firstpushbutton is in inward position and its contact member is in engagementwith its stationary contact and said second pushbutton is in outwardposition and its contact member is out of engagement with its stationarycontact, and in the other of which said second pushbutton is in inwardposition and the engagement of said contact members are reversed,resilient means urging said crossbar toward the opposite diagonalposition when either of said push buttons is pressed toward inwardposition and moves said crossbar past a lateral position with respect toits center pivot point, said resilient means comprising a coil springextending between each end of said crossbar and an adjacent portion ofsaid housing disposed transversely from the center pivot point of saidcrossbar.

2. The structure described in claim 1, the center of said crossbar beingpivotally mounted in a slot formed in said hous' ing adjacent the centerthereof and the ends of said crossbar being pivotally mounted in slotsformed adjacent the midportion of said bars.

3. The structure described in claim 2, the opposite sides of each ofsaid slots being V-shaped to form oppositely facing fulcrums for saidcrossbar.

4. The structure described in claim 3, each of said contact memberscomprising a leaf spring having a pair of laterally directed resilientwings, and a resilient stationary contact engageable with each of saidwings, said wings and stationary contacts making resilient brushingengagement with each other when said pushbuttons and contact members aremoved between inward and outward positions.

5. The structure described in claim 4, each of said stationary contactscomprising an elongated curved resilient member having a free enddisposed within said housing, said free ends being movable bothlongitudinally and transversely upon engagement thereof with the wingsof said contact members.

6. The structure described in claim 5, and a resistor mounted adjacentone of the stationary contacts engaged by each of said contact members,said resistor having one lead thereof disposed directly adjacent to saidstationary contact, the resilience of said stationary contact normallyurging it into engagement with said lead whenever its contact member isin outward position, said contact member being adapted to move saidstationary contact out of engagement with said lead when said contactmember is in inward position.

7. The structure described in claim 6, and means for connecting one ofsaid stationary contacts engageable by each of said contact members withone of a pair of television cable connections and means for connectingthe other of said stationary contacts engageable by each of said contactmembers with a television set, said pushbuttons being operable toselectively connect said television set to either of said cables, theunused cable being automatically connected through one of said resistorsto electrical ground.

8. The structure described in claim 1, and means for connecting one ofsaid stationary contacts engageable by each of said contact members withone of a pair of television cable connections, a balun transformerdisposed in said housing, means connecting the other of said stationarycontacts engageable by each of said contact members to the input of saidtransformer, and means for connecting the output of said transformer toa television set, said pushbuttons being operable to selectively connectsaid television set to either of said cables through said transformer.

1. A switch comprising a housing, first and second pushbuttons mountedfor alternating manual reciprocal movement between inward and outwardpositions with respect to said housing, an elongated bar attachment toeach of said pushbuttons, said bars extending inwardly into said housingfrom said pushbuttons, a crossbar having its center pivotally mounted ona stationary part of said housing, the ends of said crossbar beingpivotally connected to said bars, a contact member carried by the innerend of each of said bars, at least one substantially stationary contactadapted to be engaged by each of said contact members when thepushbutton to which it is attached is in inward position, said crossbarbeing movable upon the inward movement of either of said pushbuttonsbetween two stable diagonal positions, in one oF which said firstpushbutton is in inward position and its contact member is in engagementwith its stationary contact and said second pushbutton is in outwardposition and its contact member is out of engagement with its stationarycontact, and in the other of which said second pushbutton is in inwardposition and the engagement of said contact members are reversed,resilient means urging said crossbar toward the opposite diagonalposition when either of said push buttons is pressed toward inwardposition and moves said crossbar past a lateral position with respect toits center pivot point, said resilient means comprising a coil springextending between each end of said crossbar and an adjacent portion ofsaid housing disposed transversely from the center pivot point of saidcrossbar.
 2. The structure described in claim 1, the center of saidcrossbar being pivotally mounted in a slot formed in said housingadjacent the center thereof and the ends of said crossbar beingpivotally mounted in slots formed adjacent the midportion of said bars.3. The structure described in claim 2, the opposite sides of each ofsaid slots being V-shaped to form oppositely facing fulcrums for saidcrossbar.
 4. The structure described in claim 3, each of said contactmembers comprising a leaf spring having a pair of laterally directedresilient wings, and a resilient stationary contact engageable with eachof said wings, said wings and stationary contacts making resilientbrushing engagement with each other when said pushbuttons and contactmembers are moved between inward and outward positions.
 5. The structuredescribed in claim 4, each of said stationary contacts comprising anelongated curved resilient member having a free end disposed within saidhousing, said free ends being movable both longitudinally andtransversely upon engagement thereof with the wings of said contactmembers.
 6. The structure described in claim 5, and a resistor mountedadjacent one of the stationary contacts engaged by each of said contactmembers, said resistor having one lead thereof disposed directlyadjacent to said stationary contact, the resilience of said stationarycontact normally urging it into engagement with said lead whenever itscontact member is in outward position, said contact member being adaptedto move said stationary contact out of engagement with said lead whensaid contact member is in inward position.
 7. The structure described inclaim 6, and means for connecting one of said stationary contactsengageable by each of said contact members with one of a pair oftelevision cable connections and means for connecting the other of saidstationary contacts engageable by each of said contact members with atelevision set, said pushbuttons being operable to selectively connectsaid television set to either of said cables, the unused cable beingautomatically connected through one of said resistors to electricalground.
 8. The structure described in claim 1, and means for connectingone of said stationary contacts engageable by each of said contactmembers with one of a pair of television cable connections, a baluntransformer disposed in said housing, means connecting the other of saidstationary contacts engageable by each of said contact members to theinput of said transformer, and means for connecting the output of saidtransformer to a television set, said pushbuttons being operable toselectively connect said television set to either of said cables throughsaid transformer.